From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758550AbXE2OPV (ORCPT ); Tue, 29 May 2007 10:15:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752119AbXE2OPJ (ORCPT ); Tue, 29 May 2007 10:15:09 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:3243 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750838AbXE2OPH (ORCPT ); Tue, 29 May 2007 10:15:07 -0400 Date: Tue, 29 May 2007 14:14:56 +0000 From: Pavel Machek To: Theodore Tso , M Macnair , linux-kernel@vger.kernel.org Subject: Re: Seeding /dev/random not working Message-ID: <20070529141456.GC5840@ucw.cz> References: <20070529131501.GA9899@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070529131501.GA9899@thunk.org> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > I have two embedded boards (one ARM, one PowerPC), running two > > different versions of 2.6. They have no hard drives, keyboards or > > mice. They each have a NIC, but I understand these make no > > contribution to the entropy pool. > > > > if [ -f $random_seed ]; then > > cat $random_seed >/dev/urandom # should seed the pool > > fi > > dd if=/dev/urandom of=$random_seed count=1 2>/dev/null # save some > > data from urandom for next boot > > > > I have rebooted my boards many times, and after each boot I read the > > contents of $random_seed. Whilst it does not happen every time, the > > contents of $random_seed are /often the same/. To give you a feel: > > rebooted 11 times, got a total of 3 different outputs. > > Ok, so this is telling me a couple of things. First of all, if you're > only getting three outputs, it means that you don't have any > peripherals feeding entropy into the system from the boot sequence. > Without any hard drives, keyboards or mice, and a NIC whose device > driver hasn't been configured to feed entropy, you're definitely > hosed. Can we get at least time-of-boot from rtc clock to the pool? We really should not be getting identical outputs... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html